DE102019106835B4 - Rotor shaft of an electrical machine and method for manufacturing a rotor shaft - Google Patents

Abstract

Rotor shaft (1) for an electrical machine, with a supporting, tubular, metallic winding (12, 16), the winding (12, 16) being formed from wire (11) and one for supporting a rotor (24) of the electrical machine provided cylindrical middle section (2) as well as two end sections (3, 4) adjoining the middle section (2) and tapering compared to the middle section (2), the wire winding (12, 16) being single-layer, characterized in that the winding ( 12, 16) at each end section (3, 4) a bearing section (5, 6) for holding an inner ring of a bearing and at one of the end sections (4) a toothed section (9) is formed.

Description

The invention relates to a rotor shaft configured according to the preamble of claim 1 of an electrical machine, that is to say of an electric motor or generator. The invention also relates to a method for producing a rotor shaft of an electrical machine.

A rotor shaft is from the DE 22 01 443 A known. This rotor shaft is constructed as a wound piece of pipe and is part of a rotor, which should be suitable for a fast-reacting direct current motor.

The DE 10 2018 115 244 A1 discloses a method of assembling a rotor shaft for an electric motor. In this case, a laminated core is connected to the rotor shaft by hydroforming.

A method for cooling a rotor shaft of an electric motor in a motor vehicle is disclosed in US Pat DE 10 2018 101 641 B3 described. In this case, centrifugal forces are used to transport the coolant.

The JP 2002-210 019 A describes a method for manufacturing a coil for a medical instrument. A wire material is wound into a continuous coil shape.

US 2010/0 147 045 A1 discloses a flexible drilling shaft and a method for its production. The method includes winding wire to form a coil spring and applying mechanical deformation to the wire as it is wound.

The DE 453 194 A describes a hose for flexible shafts.

The JP S57-183 239 A discloses a method of making coreless double cylindrical coils by spirally winding stranded wire.

The invention is based on the object of specifying a rotor shaft for an electrical machine that has been further developed compared with the prior art, in particular with regard to manufacturing aspects.

This object is achieved according to the invention by a rotor shaft with the features of claim 1. The object is also achieved by a method for manufacturing a rotor shaft according to claim 4. In the following, in connection with the manufacturing method, the embodiments and advantages of the invention also apply mutatis mutandis to the device , that is, the rotor shaft, and vice versa.

The rotor shaft is constructed as a supporting, tubular, metallic winding made of wire and has a cylindrical middle section provided for supporting the rotor of the electrical machine and two end sections adjoining the middle section and tapering relative to the middle section.

The tapering of the end sections with respect to the central section means that both the outer diameter of each end section is smaller than the outer diameter of the central section and the inner diameter of each end section is smaller than the inner diameter of the central section. Preferably, the outside diameter of each end section is also smaller than the inside diameter of the central section of the rotor shaft.

In comparison to conventional solutions, the rotor shaft can thus be manufactured in a particularly material-saving manner, which is also associated with a low moment of inertia. According to the invention, the winding is a single-layer winding. The wall thickness of the rotor shaft corresponds to the thickness of the wire from which the winding is formed, provided that no material was removed during manufacture.

• - Wicklung eines Drahtes zu einem einlagigen, rohrförmigen Drahtrohling, welcher einen zylindrischen Mittelabschnitt sowie zwei an den Mittelabschnitt anschließende, gegenüber dem Mittelabschnitt verjüngte Endabschnitte aufweist, und Herstellung stoffschlüssiger Verbindungen zwischen Windungen des Drahtrohlings,
• - mehrstufige spanende Bearbeitung der Oberfläche des Drahtrohlings, wobei an beiden Endabschnitten Abschnitte zur Halterung von Lagerringen erzeugt werden und an einem der Endabschnitte eine zur Übertragung eines Drehmoments vorgesehene Formschlusskontur, insbesondere in Form einer Verzahnung, erzeugt wird.

The rotor shaft can be manufactured in the following steps:

• - Winding a wire into a single-layer, tubular wire blank, which has a cylindrical middle section and two end sections adjoining the middle section that are tapered with respect to the middle section, and the production of material connections between turns of the wire blank,
• Multi-stage machining of the surface of the wire blank, with sections for holding bearing rings being generated at both end sections and a form-fit contour intended for transmitting a torque, in particular in the form of a toothing, being generated at one of the end sections.

The form-fitting connections between the individual turns of the wire can either be established during the winding process or only after the winding process has been completed.

In both cases, the winding of the wire blank enables an efficient production of a near net shape blank, that is to say wire blank. There is a high degree of freedom here Shaping. In the simplest case, the entire blank, the shape of which already corresponds with a good approximation to the shape of the later rotor shaft, has a uniform wall thickness over its entire length.

The wire from which the blank is wound has, in typical configurations, a rectangular or approximately rectangular cross section. Rollers with variable spacing can be used to bend the wire, in particular ductile steel wire, into round shape, as is basically known from the manufacture of springs. The roller spacing is varied in such a way that a near-net-shape wire lap, that is to say wire blank, is produced in the form of the later rotor shaft. Due to the manufacturing process, such a wire coil has short distances between the individual turns. The winding is optionally supported by a shape-defining winding core or carried out exclusively on it.

After the wire has been wound to form the blank, the individual turns can be applied to one another in a simple manner by applying an axial force. The cohesive connection of the windings to one another is done, for example, by welding. During welding, the workpiece, that is to say the wire blank, is rotated, for example, about its own axis and, at the same time, is advanced along its axis. Alternatively, the welding tool can be advanced.

Welding can be done with or without the use of filler metals. Low-warpage processes such as laser or electron beam welding are advantageous. Preferably, the cross-section of the blank, which corresponds to the wire thickness, is approximately or completely welded through.

As an alternative to a spiral welding of the turns of the wire blank, welding only in individual areas can also be considered. Such areas can be linear, the lines not necessarily being aligned parallel to the central axis of the wire blank. It is also possible to set just individual spot welds in any pattern.

If no subsequent heat treatment of the rotor shaft is planned, the turns of the wire blank can also be connected to one another by soldering or gluing. In this case, tin solder or adhesive can be rolled or applied to the wire surfaces that will later come into contact before the blank is wound.

After the blank has been welded, glued or soldered, it is processed further in a multi-stage machining process. The multi-stage machining process preferably comprises at least one machining step with geometrically defined machining and at least one machining step with geometrically undefined chip formation. In the first machining step, the wire blank is first roughly turned in a turning process. Then, if the connections between the windings allow this with regard to their thermal load capacity, a heat treatment, for example by case hardening, can take place. Finally, the final fine machining takes place, in particular by grinding. Alternatively, finish machining is carried out with a geometrically defined cutting edge, in particular by turning machining.

In an advantageous embodiment, the finished rotor shaft has several functional areas that do not require any further processing before the rotor of the electrical machine is installed: On the one hand, there is a bearing section at each end section, which is intended to hold an inner ring of a bearing, in particular a roller bearing. In addition, a toothed section is formed directly by the winding, preferably on exactly one of the end sections, which is suitable as a fitting toothing for the torque-transmitting connection of the rotor shaft to a further machine element. In addition, further contours, for example grooves for retaining rings, can be molded into the end sections. In principle, it is also conceivable to form functional areas directly by winding the wire without post-processing.

A bearing seat provided by the rotor shaft can also be located on the inner diameter of the rotor shaft, which can be advantageous in particular in cases with limited installation space in the axial direction. In such a case, the bearing, that is to say the roller bearing, is inserted into the rotor package to save space. The rotor shaft can be essentially cylindrical in shape overall.

The winding of the rotor shaft made of wire offers a wide range of options for designing appropriate design, with only a small amount of machining being required. The wire from which the rotor shaft is wound does not necessarily have an exactly rectangular cross section. For example, the cross-section of the wire tapers outwards, with “outside” referring to the radial direction of the wound blank. The cross-section of the wire, which becomes narrower towards the outside, results in free spaces on the outer circumferential surface of the wire blank which can be used for the introduction of welding filler materials or other connecting materials.

If, on the other hand, the use of welding filler materials or a solder to be inserted between the turns is not intended, the cross-section of the wire, when it is wound, should allow full-surface contact between the individual turns if possible. The deformation of the wire on the outer circumferential surface of the blank causes a cross-section reduction in this area compared with the initial state of the wire. To compensate for this effect, a wire with a trapezoidal cross-section in the initial state can be used, the trapezoidal shape being designed in such a way that the bending of the wire results in an approximation of a rectangular cross-sectional shape.

Likewise, a wire can be used to produce the blank, the flanks of which have form-fitting contours in the form of strip-shaped elevations and corresponding depressions which interlock with the corresponding contours of adjacent turns within the finished blank.

Regardless of the cross-sectional configuration of the wire, it can be designed either as a solid or as a hollow wire. In the case of a hollow wire, coolant or lubricant can be passed through this. Even in cases in which a hollow wire is not used as a line for a fluid, the hollow design contributes to a weight-saving construction of the rotor shaft.

The cross section of the wire is not necessarily constant over its entire length. For example, sections of the rotor shaft with high stress are made with a wire that is thicker in the radial direction - in relation to the cylindrical shape of the rotor shaft - than sections of the rotor shaft with lower stress.

If the rotor shaft has differently profiled wire sections, such sections can be separated from different wire coils and placed next to one another in the course of production. Alternatively, it is possible to produce a wire which, in the form of a “tailored wire”, has different wire cross-sections in a single wire strand, so that attachment points, which are necessary when using different wires, are omitted. A device for rolling such a wire with different cross-sections in sections can be integrated into the system for manufacturing the rotor shaft. In this way, all steps from the forming of the wire to the finishing of the bearing seats and a toothing are implemented in one and the same production system.

The rotor shaft is particularly suitable for use in a permanent magnet-excited electric motor of an electric vehicle. Due to the one-piece, load-appropriate design, there is a weight saving of around 50% compared to conventional hollow shafts of electric motors. In typical embodiments, the rotor shaft is a steel part that is not used as part of the magnetic circuit of the electric motor. In a preferred embodiment, there are no openings whatsoever, for example in the form of slots or bores, on the entire circumferential surface of the rotor shaft, that is, both within the middle section and within the end sections adjoining this.

The closed-walled, one-piece design of the rotor shaft favors a particularly thin-walled and at the same time mechanically highly resilient design. At the same time, the manufacture of the rotor shaft from steel, compared to shafts from aluminum, ensures particularly small temperature-related dimensional changes, even when used in an electric motor with high power density. Optionally, another shaft, which is either also a hollow shaft or a solid shaft, is arranged concentrically within the rotor shaft.

• 1 einen zur Herstellung einer Rotorwelle vorgesehenen Drahtrohling,
• 2 ein Detail des Drahtrohlings nach 1,
• 3 den Drahtrohling im geschweißten Zustand,
• 4 ein Detail der Anordnung nach 3,
• 5 bis 7 den zu einer Rotorwelle weiter verarbeiteten Drahtrohling,
• 8 bis 13 verschiedene Querschnitte von Drähten, welche zur Herstellung einer Rotorwelle geeignet sind,
• 14 in schematisierter Darstellung eine Rotorwelle samt Rotor eines Elektromotors.

Several exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show here:

• 1 a wire blank intended for the production of a rotor shaft,
• 2 a detail of the wire blank after 1 ,
• 3 the wire blank in the welded state,
• 4th a detail according to the arrangement 3 ,
• 5 to 7th the wire blank processed into a rotor shaft,
• 8th to 13 different cross-sections of wires which are suitable for manufacturing a rotor shaft,
• 14th a schematic representation of a rotor shaft together with the rotor of an electric motor.

Unless otherwise stated, the following explanations relate to all exemplary embodiments. Parts and contours which correspond to one another or have the same effect in principle are identified by the same reference symbols in all figures.

A rotor shaft 1 is intended for use in an electric motor, which for example as a traction motor of a motor vehicle for Use comes. The rotor shaft 1 only carries you in 14th indicated rotor 24 , which one with magnets 25th is equipped. With the magnets 25th it is permanent magnets, which are in a laminated core, which the rotor shaft 1 surrounds are included. The rotor 24 is part of a brushless DC motor. Alternatively, the rotor shaft can be used 1 in an asynchronous motor into consideration, the rotor shaft 1 in this case carries a rotor which is provided with conductor bars and short-circuit rings.

The rotor shaft 1 is completely made of one wire 11 , namely steel wire, wound in a single layer. From the wire 11 is first a wire blank 12 wrapped in the 1 and 2 is shown. The individual turns of the wire blank 12 , i.e. the winding, are with 13 designated. Between the individual turns 13 exist in this processing state column 14th .

After winding the wire blank 12 , if necessary, compressed by a processing machine, i.e. approximately to the length of the later rotor shaft 1 brought. The individual turns 13 of the wire blank 12 are welded together. One with 15th designated weld, commonly referred to as filling, is in 4th recognizable. The whole, with 16 designated, welded blank, which like the not yet welded blank 12 represents a winding is in 3 pictured.

In the further, multi-stage, machining, the blank, which has already been manufactured near net shape 16 to the rotor shaft 1 further processed. As with the unwelded wire blank 12 and with the welded blank 16 recognizable, the rotor shaft 1 a cylindrical central portion 2 and two end sections 3 , 4th with opposite the middle section 2 reduced diameter. The reduction relates to both the inside diameter and the outside diameter of the sections 2 , 3 , 4th .

Each end section 3 , 4th has a storage section 5 , 6th on, which acts as a seat for an inner ring of a rolling bearing. Only in the second end section 4th becomes a gear section 9 generated, which for the torque-transmitting connection between the rotor shaft 1 and another rotating element can be used. The toothed section 9 is immediately through the wire 11 and is formed just like the storage sections 5 , 6th commonly referred to as a functional section. Within the functional sections 5 , 6th , 9 there are different grooves 7th , 8th , 10 , which can be used to hold retaining rings.

The wire 11 , from which the rotor shaft 1 after 5 is made, has a rectangular cross-section, as in FIG 8th shown. That surface of the wire 11 , which will later be the outer peripheral surface of the rotor shaft 1 including the functional sections 5 , 6th , 9 forms is called the outer surface 17th designated. The outer surface 17th lies an inner surface 18th across from. The two the surfaces 17th , 18th connecting flanks of the wire 11 are with 19th , 20th designated.

Another possible cross-sectional shape of a wire 11 is in 9 outlined. In this case a wire blank with thinner walls is produced 12 , 16 and accordingly also a thinner-walled rotor shaft 1 . In a manner not shown, within a single rotor shaft 1 a first line 11 with the in 8th shown square cross-section with a second wire 11 with the in 9 be connected rectangular, non-square cross-sectional shape shown. Here, the thicker cross-section is 8th for areas of the rotor shaft that are subject to particularly heavy mechanical loads 1 or for areas in which a relatively high machining volume occurs compared to other areas. In particular, these areas are the functional sections 5 , 6th , 9 .

The various cross-section variants according to the 8th and 9 realized by one and the same wire strand. The rolling of the wire 11 , which has a cross-section that varies over its length, is carried out in this case by a system, which the winding device in which the wire blank 12 is generated, is connected immediately upstream.

The 10 shows a trapezoidal cross section of a wire 11 , the trapezoidal shape is shown exaggerated. It is not yet shown for the wire blank 12 coiled wire 11 . The outer surface 17th is wider than the inner surface in this state 18th . The winding causes the wire to be stretched 11 on the outer peripheral surface of the wire blank 12 what with a reduction in the width of the outer surface 17th is equivalent. This approximates the cross-sectional shape of the wire 11 in the desired way of the rectangular shape.

The cross-sectional design of the wire 11 after 11 is particularly suitable for the production of a welded blank 16 . In this case are to the outer surface 17th bordering sections of the flanks 19th , 20th so inclined that the cross section of the wire 11 to the outer surface 17th narrowed down. This leaves the wire blank even when the wire blank is compressed 12 column 14th which by a weld seam 15th can be filled out.

The in 12 shown wire 11 is designed as a hollow wire. A cavity within the wire 11 is with 21st and can be used to convey coolant or lubricant, which means the entire wire 11 forms a liquid line. The outer contour of the wire 11 after 12 corresponds to the embodiment according to 8th . Alternatively, the wire 11 after 12 for example accordingly 10 or 11 be profiled.

The in 13 shown wire 11 it is again a solid wire, with a cavity not shown in this case as well 21st , that is, channel, the wire 11 can pull through. In case of 13 shows every flank 19th , 20th a concave or convex form-fit contour 22nd , 23 on, which means within the completed rotor shaft 1 a form fit to adjacent turns 13 is made.

List of reference symbols

1

Rotor shaft

2

Middle section

3

first end section

4th

second end section

5

Storage section

6th

Storage section

7th

Groove

8th

Groove

9

Gear section

10

Groove in the toothed section

11

wire

12

Wire blank, winding

13

Twist

14th

gap

15th

Filling, weld seam

16

welded blank

17th

outer surface

18th

inner surface

19th

Flank

20th

Flank

21st

cavity

22nd

Form-fit contour

23

Form-fit contour

24

rotor

25th

magnet

Claims (10)

Rotor shaft (1) for an electrical machine, with a supporting, tubular, metallic winding (12, 16), the winding (12, 16) being formed from wire (11) and one for supporting a rotor (24) of the electrical machine provided cylindrical middle section (2) as well as two end sections (3, 4) adjoining the middle section (2) and tapering compared to the middle section (2), the wire winding (12, 16) being single-layer, characterized in that the winding ( 12, 16) at each end section (3, 4) a bearing section (5, 6) for holding an inner ring of a bearing and at one of the end sections (4) a toothed section (9) is formed. Rotor shaft (1) Claim 1 , characterized in that the bearing is a roller bearing. Rotor shaft (1) Claim 1 or 2 , characterized in that the wire (11) has a non-uniform cross section over its length. Method for manufacturing a rotor shaft (1) of an electrical machine, with the following steps: - Winding of a wire (11) into a single-layer, tubular wire blank (12, 16) which has a cylindrical central section (2) and two end sections (3, 4) adjoining the central section (2) and tapering relative to the central section (2) , and production of material connections between turns (13) of the wire blank (12, 16), - Multi-stage machining of the surface of the wire blank (12, 16), with sections (5, 6) for holding bearing rings being produced at both end sections (3, 4) and a contour provided for transmitting a torque at one of the end sections (4) is produced. Procedure according to Claim 4 , characterized in that the contour is generated in the form of a toothing (9). Procedure according to Claim 4 or 5 , characterized in that a wire (11) with a rectangular cross-section is used to produce the wire blank (12, 16). Procedure according to Claim 4 or 5 , characterized in that the wire blank (12, 16) is wound from wire (11), the cross section of which tapers outward in the radial direction of the wire blank (12, 16). Procedure according to Claim 4 or 5 , characterized in that a wire (11) with a trapezoidal cross-section in the non-bent state is used, the wire cross-section being approximated to a rectangular shape due to the bending which occurs during winding. Procedure according to Claim 4 or 5 , characterized in that the wire blank (12, 16) is wound from wire (11), the flanks (19, 20) of which have interlocking contours (22, 23) that mesh with adjacent wire windings (13). Method according to one of the Claims 4 to 9 , characterized in that the wire blank (12, 16) is wound from hollow wire (11).

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